T3

You should get a T3 test if you have symptoms of hyperthyroidism, such as weight loss, palpitations, anxiety, sweating, or tremors, or of hypothyroidism, such as fatigue, weight gain, or cold intolerance. It is also recommended when TSH is abnormal, and for monitoring thyroid treatment or Graves' disease.

No special preparation or fasting is required for a T3 test. Give your sample in the morning, and take your thyroid medicine after the sample unless your doctor advises otherwise. Stop biotin supplements 48–72 hours before the test, as biotin can interfere with results. Inform your doctor about pregnancy, oral contraceptives, or steroids.

No, fasting is not required for a T3 test. You can eat and drink normally before giving your sample. A morning sample is preferred, and you should take your thyroid medicine after the test unless your doctor advises otherwise. Stop biotin supplements 48–72 hours beforehand, as biotin can affect results.